Such coolant pumps serve to control a flow rate of the delivered coolant in an internal combustion engine to prevent the overheating thereof. These pumps are usually driven via a belt or chain drive so that the coolant pump impeller is driven at the speed of the crankshaft or at a fixed ratio to the speed of the crankshaft.
In modern internal combustion engines, the delivered coolant flow must be matched with the coolant demand of the internal combustion engine or the motor vehicle. The cold running phase of the engine should in particular be reduced to prevent increased pollutant emissions and to reduce fuel consumption. This is realized, inter alia, by restricting or completely switching off the coolant flow during this phase.
Various pump designs for controlling coolant flow rate are known. Besides electrically driven coolant pumps, pumps are known which can be coupled to or decoupled from their drive units via couplings, in particular hydrodynamic couplings. A particularly inexpensive and simple manner of controlling the delivered coolant flow is the use of an axially movable control slide which is pushed across the coolant pump impeller so that, for reducing the coolant flow, the pump does not deliver into the surrounding delivery duct, but against the closed slide.
The control of this slide is also performed in different ways. Besides a purely electric adjustment, a hydraulic adjustment of the slides has proved particularly successful. A hydraulic displacement is in most cases carried out via an annular piston chamber which is filled with a hydraulic fluid and whose piston is connected to the slide so that the slide is moved across the impeller during a filling of the chamber. The slide is returned by opening the piston chamber towards an outlet, in most cases via a magnetic valve as well as via a spring action providing the force for returning the slide.
In order for the coolant flow required to move the slide not to be supplied via additional delivery units, such as additional piston/cylinder units, or for other hydraulic fluids not to be compressed for operating purposes, mechanically controllable coolant pumps are known on whose drive shaft a second delivery wheel is arranged via which the pressure for adjusting the slide is provided. These pumps are, for example, designed as side channel pumps or servo pumps.
A coolant system having a side channel pump acting as a secondary pump is described in DE 10 2012 207 387 A1. A slide is here located on the rear side of the pump, which slide is movable via a pressure in a ring chamber and which can be returned by a spring. The ring chamber is formed in a housing which is disposed on the rear side of the slide and in which a first side channel of the side channel pump is arranged that is accordingly disposed opposite to the side channel pump impeller arranged on the shaft. A second side channel is formed in another housing part on the side opposite to the side channel pump impeller. Via a 3/2-way valve in this pump, in a first position, a discharge side of the side channel pump is closed and a suction side of the pump is connected to the coolant circuit and the slide, and, in a second position, the discharge side is connected to the ring chamber of the slide and the suction side is connected to the coolant circuit. A detailed duct and flow routing is not described. In modern internal combustion engines, the schematically shown flow routing for this pump can only be realized with an increased technical effort. This also involves an increased assembly effort and, above all, a larger installation space for the schematically shown flow routing and due to the selected arrangements and the split design of the housing so that such a pump cannot be arranged and installed in a corresponding arrangement of a cylinder crankcase.